Limehouse

Water rich in calcium carbonate forms stalactites, stalagmites and ultimately pillars in caves due to gradual crystallisation of the solute. Most conventional methods of construction involve moving massive blocks of stone, brick or composite minerals around. The process whereby pillars form in caves could also be used in building. A relatively lightweight but sufficiently strong frame of the appropriate form could be doused constantly in water which is a saturated solution of calcium carbonate or other appropriate mineral, and gradually a "natural" building would form in one piece. The process could be accelerated by the use of heat and dehumidification to increase the rate of evapouration, and perhaps also by catalysts on the framework. After the building is complete, the framework could be removed, leaving a cave-like construction, with appropriate gaps for windows, doors and conduits, which would be stronger than a structure made from bricks or otherwise built from smaller components, which would also look like something designed by Gaudi. This could then be painted with a waterproof substance which slowed further action by the elements that would otherwise dissolve the building.